This invention relates to a method for producing polyalkylene-grafted poly(alkenyl benzene-co-maleimide) polymers and the use of such polymers, when oil extended, in producing high damping materials.
Two or more polymers may be blended together to form a wide variety of random or structured morphologies to obtain products that offer potentially desirable combinations of characteristics. However, many potential combinations may be difficult or even impossible to achieve in practice through simple blending. Frequently, the polymers are thermodynamically immiscible, which precludes generating a truly homogeneous product. This immiscibility is not a problem where a two-phase structure is desirable; however, the interactions (or lack thereof) at the interface between the two phases very often lead to problems. For example, high interfacial tension and poor adhesion between the phases is common. The interfacial tension, along with high viscosities, contributes to the inherent difficulty of imparting the desired degree of dispersion to such random mixtures and to their subsequent lack of stability. This gives rise to gross separation or stratification during later processing or use. Poor adhesion leads in part to the weak and brittle mechanical behavior often observed in dispersed blends and may render useless some highly structured morphologies.
Free-radically initiated polymerizations of maleic anhydride with vinyl monomers, such as styrene and isobutylene, are known. Further, imidization of maleic anhydride with a primary amine group also is known.
Monofunctional N-alkyl and N-aryl maleimides have been used extensively to improve the heat stability of (co)polymers prepared from vinyl monomers. In one method, maleimides are first reacted with bulk resin(s) such as, for example, ABS (poly(acrylonitrile-co-butadiene-co-styrene)); blends of poly(acrylonitrile-co-butadiene) and poly(styrene-co-acrylonitrile); PVC (poly(vinyl chloride)); SAN (poly(styrene-co-acrylonitrile)); PMMA (poly(methyl methacrylate)); and the like. The copolymers formed are then reacted with monomers, such as styrene or acrylonitrile. However, a more preferred industrial practice is to make copolymers of maleimides with other monomers, such as styrene and optionally acrylonitrile, and to blend the copolymer with a resin, such as an ABS or SAN resin. In any event, the polymer compositions are adjusted so that the copolymers are fully compatible with the bulk resins as shown by the presence of a single glass transition point via, e.g., differential scanning calorimetry (DSC).
A batch method for preparing a grafted copolymer having the impact strength of polypropylene and the elastomeric properties of a block copolymer but which avoids the above-referenced problems remains desirable.